Package: emacs;
Reported by: Matthew Malcomson <hardenedapple <at> gmail.com>
Date: Fri, 24 Mar 2023 13:42:02 UTC
Severity: normal
Found in version 28.2
Done: Stefan Kangas <stefankangas <at> gmail.com>
Bug is archived. No further changes may be made.
Message #14 received at 62419 <at> debbugs.gnu.org (full text, mbox):
From: Stefan Monnier <monnier <at> iro.umontreal.ca> To: Matthew Malcomson <hardenedapple <at> gmail.com> Cc: 62419 <at> debbugs.gnu.org Subject: Re: bug#62419: 28.2; Elisp let-bound buffer-local variable and kill-local-variable Date: Sun, 26 Mar 2023 10:01:48 -0400
> (setq auto-fill-function 'local-symbol)
> (describe-variable 'auto-fill-function)
> ;; `auto-fill-function' is let-bound in the buffer scope
> (let ((auto-fill-function 'temp-symbol))
> ;; Now there is no buffer-local variable for `auto-fill-function', but the
> ;; `let' unwrapping info is still there.
> (kill-local-variable 'auto-fill-function)
> ;; Since the check in the emacs source is
> ;; a) Is there a buffer-local variable.
> ;; b) Is there a let-binding shadowing the current variable.
> ;; Then this `setq' sets the *global* variable.
> (setq auto-fill-function 'other-symbol))
> ;; Exiting the `let' has special handling to avoid resetting a local variable
> ;; when the local variable was `let' bound, which means that overall the `setq'
> ;; set the global variable and the `let' has been lost.
AFAIK the behavior is "as intended": the `let` only affects *one*
binding, either the global one or the buffer-local one.
> AIUI the minor mode is usually turned on outside of any let binding, but the
> described situation happens due to an edge-case:
> - `newline` let-binds `auto-fill-mode`
> - Visited file has changed outside of Emacs, so user is queried whether to
> `revert-buffer` while in `newline`
> - `revert-buffer` calls `normal-mode`, which runs `kill-all-local-variables`
> - Later, `yasnippet-mode` is turned on and the `setq` is evaluated.
The "`newline` let-binds `auto-fill-mode`" seems like the source of the
problem :-(
As for yasnippet.el, I suspect that I patch like the one below would
avoid the problem.
Stefan
diff --git a/yasnippet.el b/yasnippet.el
index 78ef38ac39..98124c7a61 100644
--- a/yasnippet.el
+++ b/yasnippet.el
@@ -860,10 +828,9 @@ which decides on the snippet to expand.")
"Hook run when `yas-minor-mode' is turned on.")
(defun yas--auto-fill-wrapper ()
- (when (and auto-fill-function
- (not (eq auto-fill-function #'yas--auto-fill)))
- (setq yas--original-auto-fill-function auto-fill-function)
- (setq auto-fill-function #'yas--auto-fill)))
+ (when auto-fill-function ;Turning the mode ON.
+ (cl-assert (local-variable-p 'auto-fill-function))
+ (add-function :around (local 'auto-fill-function) #'yas--auto-fill)))
;;;###autoload
(define-minor-mode yas-minor-mode
@@ -906,8 +873,8 @@ Key bindings:
;; auto-fill handler.
(remove-hook 'post-command-hook #'yas--post-command-handler t)
(remove-hook 'auto-fill-mode-hook #'yas--auto-fill-wrapper)
- (when (local-variable-p 'yas--original-auto-fill-function)
- (setq auto-fill-function yas--original-auto-fill-function))
+ (when (local-variable-p 'auto-fill-function)
+ (remove-function (local 'auto-fill-function) #'yas--auto-fill))
(setq emulation-mode-map-alists
(remove 'yas--direct-keymaps emulation-mode-map-alists)))))
@@ -3880,7 +3847,7 @@ field start. This hook does nothing if an undo is in progress."
snippet (yas--snippet-field-mirrors snippet)))
(setq yas--todo-snippet-indent nil))))
-(defun yas--auto-fill ()
+(defun yas--auto-fill (orig-fun &rest args)
;; Preserve snippet markers during auto-fill.
(let* ((orig-point (point))
(end (progn (forward-paragraph) (point)))
@@ -3897,44 +3864,7 @@ field start. This hook does nothing if an undo is in progress."
reoverlays))
(goto-char orig-point)
(let ((yas--inhibit-overlay-hooks t))
- (if yas--original-auto-fill-function
- (funcall yas--original-auto-fill-function)
- ;; Shouldn't happen, gather more info about it (see #873/919).
- (let ((yas--fill-fun-values `((t ,(default-value 'yas--original-auto-fill-function))))
- (fill-fun-values `((t ,(default-value 'auto-fill-function))))
- ;; Listing 2 buffers with the same value is enough
- (print-length 3))
- (save-current-buffer
- (dolist (buf (let ((bufs (buffer-list)))
- ;; List the current buffer first.
- (setq bufs (cons (current-buffer)
- (remq (current-buffer) bufs)))))
- (set-buffer buf)
- (let* ((yf-cell (assq yas--original-auto-fill-function
- yas--fill-fun-values))
- (af-cell (assq auto-fill-function fill-fun-values)))
- (when (local-variable-p 'yas--original-auto-fill-function)
- (if yf-cell (setcdr yf-cell (cons buf (cdr yf-cell)))
- (push (list yas--original-auto-fill-function buf) yas--fill-fun-values)))
- (when (local-variable-p 'auto-fill-function)
- (if af-cell (setcdr af-cell (cons buf (cdr af-cell)))
- (push (list auto-fill-function buf) fill-fun-values))))))
- (lwarn '(yasnippet auto-fill bug) :error
- "`yas--original-auto-fill-function' unexpectedly nil in %S! Disabling auto-fill.
- %S
- `auto-fill-function': %S\n%s"
- (current-buffer) yas--fill-fun-values fill-fun-values
- (if (fboundp 'backtrace--print-frame)
- (with-output-to-string
- (mapc (lambda (frame)
- (apply #'backtrace--print-frame frame))
- yas--watch-auto-fill-backtrace))
- ""))
- ;; Try to avoid repeated triggering of this bug.
- (auto-fill-mode -1)
- ;; Don't pop up more than once in a session (still log though).
- (defvar warning-suppress-types) ; `warnings' is autoloaded by `lwarn'.
- (add-to-list 'warning-suppress-types '(yasnippet auto-fill bug)))))
+ (apply orig-fun args))
(save-excursion
(setq end (progn (forward-paragraph) (point)))
(setq beg (progn (backward-paragraph) (point))))
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